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Biomedical subjects

M G McGee

Publications and source records attributed to M G McGee.

At least 37 records · Page 2Linked to original sources
PubMed1980

Quantitative indices of intra-aortic balloon pump (IABP) dependence during post-infarction cardiogenic shock.

This study attempts to quantitate post-infarction cardiogenic shock IABP dependence in instances of massive myocardial infarction with the use of hemodynamic indices plotted over time-course trajectories. Mortality is predicted when age and hemodynamic performance are also considered. It appears that post-infarction IABP dependence can be quantitated and that such information can be useful in considering diagnostic and therapeutic alternatives during the course of IABP support and cardiogenic shock. The analysis suggests that such IABP-dependent patients could be considered for therapeutic alternatives. They do not expire during the first 50 hours of IABP support and neither improve nor deteriorate during the second 50 hours of support. They remain in Class B without the occurrence of life-threatening ventricular dysrhythmias for a sufficient time for cardiac catheterization to determine the appropriateness of corrective procedures.

Adult↗
PubMed1979

RIGHT AND LEFT VENTRICULAR HEMODYNAMIC INDICES AS PREDICTORS OF THE NEED FOR AND OUTCOME OF POST-CARDIOTOMY MECHANICAL INTRAAORTIC BALLOON PUMP SUPPORT.

Preoperative cardiac catheterization data of 21 patients requiring intraaortic balloon pumping (IABP) for weaning from cardiopulmonary bypass were analyzed and compared with similar data in 28 patients who underwent nearly similar operative procedures, but did not require IABP for weaning. Cardiac index (CI) and systemic vascular resistance (SVR) were found to have predictive value for the need of IABP for weaning from cardiopulmonary bypass and differentiated survival from non-survival. Left ventricular end diastolic pressure (LVEDP) was not found to be predictive. Ejection fraction (EF) was significantly lower in those who required IABP than those who did not; EF did not predict the outcome. Pulmonary capillary wedge pressure ([unk]), pulmonary artery pressure ([unk]) and pulmonary vascular resistance (PVR) were predictive of the need for IABP, but not the outcome. Left ventricular minute work index (LVMWI) was significantly lower in those requiring IABP, right ventricular minute work index (RVMWI) was predictive of survival with IABP. Together, LVMWI and RVMWI were predictive of the need for and outcome of IABP following cardiopulmonary bypass. Twenty-seven of 28 control RVMWI's were normal. No patient requiring IABP had depressed RVMWI's preoperatively. Elevated preoperative RVMWI's were associated with 80% survival with postcardiotomy IABP; normal RVMWI's were associated with a 56% survival with post-cardiotomy IABP. Elevated preoperative RVMWI's reflected moderate to maximal right ventricular compensatory capacity in response to depressed left ventricular function. Normal preoperative RVMWI's in the presence of depressed LVMWI's were indicative of decreased right ventricular compensatory capacity in post-cardiotomy IABP-support settings. Right ventricular function is as important as left ventricular function as a prognosticator for the need and outcome of IABP support of the failing post-cardiotomy circulation.

Journal Article↗
PubMed1979

CLINICAL TRIALS OF THE ABDOMINAL LEFT VENTRICULAR ASSIST DEVICE (ALVAD): PROGRESS REPORT.

An abdominal left ventricular assist device (ALVAD) is undergoing controlled clinical trials in our institution. The ALVAD is pneumatically-actuated, synchronously or asynchronously with an external console and is interposed between the apex of the left ventricle and the infrarenal abdominal aorta. It is an order of magnitude more effective than conventional intraaortic balloon pumping. Thus far, we have implanted this pump in 21 patients (15 males and six females). The average age has been 50. The duration of cardiopulmonary bypass with intensive pharmacologic support and IABP until ALVAD implantation has been nearly 4 hours. The plasma hemoglobins prior to ALVAD implantation have averaged 168 mg%. The platelet counts at implantation have averaged 68,000 mm(3). The average duration of ALVAD support has been in excess of one day and the longest trial extended for one week. We have been able to remove the pump after ventricular recovery in two instances and effected cardiac allografting in one instance of ALVAD dependency. We have found that (1) the profoundly depressed left (and right) ventricles can recover if totally supported with this device; (2) the device can function in the presence of ventricular fibrillation and/or standstill; (3) the device can effectively replace both left and right ventricular function in the presence of normal pulmonary vascular resistance and microcirculatory hemodynamics; and (4) in the presence of impending multiple organ failure, procrastination in use is to be avoided.

Journal Article↗
PubMed1978

Handedness and mental rotation.

Handedness and mental rotation test scores were examined by sex and generation for 801 individuals in 200 families. An orderly relationship between bilateralization of function on the hand preference task and mental rotation test scores was found.

Adult↗
PubMedDate not supplied

Extended clinical support with an implantable left ventricular assist device.

Clinical evaluations are under way of an intracorporeal (abdominally positioned) pulsatile left ventricular assist device (LVAD) that is capable of providing support for extended periods (greater than 30 days) in patients awaiting heart transplantation. The LVAD, developed by Thermo Cardiosystems Inc. (Woburn, MA), has uniquely textured blood contacting surfaces and requires only minimal antithrombotic therapy. It has been used at the Texas Heart Institute as a bridge to transplantation in 11 patients, including 2 who are currently receiving support. Four patients required extended LVAD support (35-132 days); of those, three are doing well at 1.5, 8.5, and 13 months, respectively, after transplantation, and one died of liver failure 49 days after transplantation. The LVAD was operated in a fixed-rate mode to maintain pump flows at 4-8 L/min, resulting in stabilization of hemodynamic and secondary organ function in all patients. Blood chemistry and hematologic values returned to normal during LVAD support in three of four patients. Postoperative anticoagulation was gradually reduced over the course of the trials. The two most recent patients (35 and 132 days) received only oral dipyridamole (75 mg X 3/day) and aspirin (80 mg/day) after the early recovery period (four-six days), resulting in normal prothrombin and partial thromboplastin times. Plasma hemoglobin levels remained within acceptable limits, and there was no evidence of thromboembolism. Blood contacting surfaces were coated with a thin, adherent, biologically derived lining. The initial results indicate that the intracorporeal LVAD, with textured blood contacting surfaces, can effectively support the failing heart for extended periods (greater than 30 days) with minimal antithrombotic therapy.

Adult↗
PubMedDate not supplied

Anatomic considerations for abdominally placed permanent left ventricular assist devices.

To determine anatomic parameters for a permanent, electrically actuated left ventricular assist device (LVAD), the effects of abdominal placement of pneumatic LVADs used as temporary support for patients awaiting heart transplantation was studied. Understanding the anatomic constraints imposed by the abdominal viscera in LVAD placement is crucial, because improper placement can result in compression or obstruction of adjacent structures. Anatomic compatibility was assessed in four men (age 22-48 years) who were supported by the LVAD for over 1 month (range 35-132 days). The pump was intraperitoneally placed in the left upper quadrant. Radiographic techniques were employed, including CT scanning (with patients supine) and contrast imaging (patients in anatomical position), and the pump and conduits appeared to be properly positioned, with minimal compression of the body of the stomach, and no obstruction of adjacent organs. Three patients returned to a solid food diet and exercised daily by stationary cycling and walking. No signs of migration or erosion of the pump were present at the time of LVAD removal and cardiac transplantation. Successful clinical experience with short-term use of the LVAD suggests that the electrically actuated device can be well tolerated in patients requiring permanent left ventricular assistance.

Abdomen↗
PubMedDate not supplied

Surface texturing and coating of biomaterial implants: effects on tissue integration and fibrosis.

To determine whether texturing and coating have additive effects in promoting tissue integration and inhibiting fibrosis, we evaluated smooth silicone rubber (SSR), textured silicone rubber (TSR), porous silicone rubber (PSR), expanded polytetrafluoroethylene (ePTFE), and porous polyurethane (PPU) subcutaneous implants in eight minipigs. Some of the implants were coated with type IV collagen (Col) and/or fibronectin (Fn). At 6 months, we removed the implants and examined them microscopically. Texturing was more important than Col and Fn in reducing fibrosis and inflammation. The PSR yielded the best response, including reduced fibrosis and inflammation, satisfactory adherence, and no dystrophic mineralization.

Animals↗
PubMedDate not supplied

Frequency and significance of infections in patients receiving prolonged LVAD support.

Infections in patients undergoing mechanical circulatory support as a bridge to transplant are associated with significant mortality and morbidity. To determine the frequency and effects of infection during such procedures, a retrospective analysis was done of 14 patients who received prolonged (greater than 14 days) support with the Heartmate left ventricular assist device (LVAD) (Thermo Cardiosystems, Inc., Woburn, MA). All patients were men (mean age, 44.3 years), and duration of LVAD support ranged from 19 to 233 days (mean, 98.1 days). During LVAD support, five patients had no infections, and, in the remaining nine patients, infections were most common in the respiratory tract, catheter tips, and urine. Four device related infections occurred in three patients, all of which were resolved with antibiotic therapy. All 14 patients underwent transplantations, and none of the operations was delayed because of infection. Eleven of the patients are long-term survivors (range of time after transplant, 7.5-37 months). Infections were not associated with mortality or significant morbidity in this group of patients.

Adult↗